Telephone system



Filed Jul 51. 1930 2 Sheets-Sheet NXURQMS lNVENTUR FE L. STU/(ELY Mamh22, 1932. V R 1 STOKELY 1,850,608

TELEPHONE SYSTEM Filed July 31, 1930 2 Sheets-Sheet 2 //v VENTUE E. L.STCJKELV Patented lVlar. .22, 1932 UNITED. 'srA ra-s PATENT orr ca V RAYL. STOKELY, F FLOR-AL PARK, NEW YORK, ASSIGNOR TO BETIL TELEPHONE LABO-RATORIES, INCORPQEATED', OF NEW YORK, N. Y., A CORPORATION OF NEW YORKTELEPHONE sYsTEur Application filed July 31,

operating magnets in the first and succeeding selector switches and theconnector switch may be located in the first selector switch. In theseprior systems theringing and busy CA: l

tone equipments may also be located in a preceding switch.

It is a'feature of this invention to provide in a'switcha pulsing relayarrangement in which the holdingrelay is maintained operated'by means ofa locking winding under control of the operating magnets of said switch;7

It is another feature of this invention to provide in systems where thecontrol equipment for a train of switches is located in a precedingswitch, means whereby the locking winding of the holding relayiscontrolled by the operating magnets in succeeding switches in the train,as they are connected during the process of establishing a connection.

Another feature relates to the selection and application of party linesignaling currents of different characteristics and comprises;

means whereby battery and ground connections onthe tip and ringconductors respectively or vice versa are established to the precedingswitch, in which the signal selecting equipment is located, by theselection of the group in which an idle succeeding switch is found andover which a connection'is'estab lished; means whereby the particularbattery and ground connection selected cause signaling current of acorresponding characteristic to be applied, and means whereby theselected signal appliedtothe connected party line 1930. Serial No.471,976.

in response to the removal of battery and ground from the conductorswhen the connection is completed to this line.

Another feature relates to the application of busy tone to the callingline and comprises means whereby battery and ground are momentarilydisconnected from the-tip and ring conductors leading to a precedingswitch when the line to which the connection has i been extended is busyand means whereby said momentary 'removal and subsequent shows a calledfour-partyline in diagram- 7 matic form.

Referring to these drawings, a description will now be made of a callfrom the calling subscriber at 1 through line finder LF, selec tor S,selector S1, connector G, and a subscriber on a line 100. When thecalling subscriber at 1 has been connected through line finder LF in theusual manner a circuit is com- I pleted throughthe subscribersloopfrombattery and ground, windings of'relay 3, arma tures and backcontacts of relay 4, and the tip and ring conductors connected to thissubscribers loop. Relay 3 operates in this circuit and closes a circuitfor the operation of relay 5 from battery impedance coil 7, fourth lowerarmature and back contact of relay 8, left hand winding of relay 5 toground at the left-hand armature and front contact of relay 3. Relay 3in operating also closes a circuit for the operation of relay 8 frombattery, winding of relay 8,-third lower armature and back contact ofrelay 9 to ground at the left hand armature and front contact of relay8. Ground is also supplied for this circuit through right hand armatureand front contact of relay 5. Relay 8 in operating closes a circuit asfollows: battery, winding of vertical magnet 11, second lower armatureand back contact of relay 9, inner lower armature and front contact ofrelay 8, winding of relay 10,1eft-hand winding of relay 5 to ground atthe left hand armature and front contact of relay 3. The vertical magnetand relay do not operate in this circuit.

When relay 3 is released at the first impulse received from the callingsubscriber to select the desired subscribers line the so called helprelay 13 is operated over a circuit from battery, right hand winding ofthis relay, right hand armature and back contact of relay 3 to ground atthe right hand armature and front contact of relay 5. Relay 13 inoperating closes a locking circuit for itself and for relay 5 frombattery, left hand winding of relay 13, right hand winding of relay 5,right hand armature and front contact of relay 13, second lower armatureand front contact of relay 8, armature and back contact of he verticalmagnet 11 to ground at the upper inner armature and back contact ofrelay 9. Relay 3 in releasing also shunts the left hand Winding of relay5 by applying ground through the left hand armature and back contact ofrelay 3 and the left hand armature and front contact of'relay 5 to oneend of the left hand winding of relay 5. It should be noted that theopposite end of the left hand winding of relay 5 is connected to groundat the right hand armature and front contact of relay 5. The inductivekick produced by this shunting of the left hand winding of relay 5serves to make relay 5 slow-to-release. It should be noted that on therelease of relay 3 a circuit is completed for the vertical magnet 11 andrelay 10, eliminating the left hand winding of relay 5, to groundthrough the left hand armature and back contact of relay 3 and left handarmature and front contact of relay 5 The relay 10 and the verticalmagnet will operate in this circuit, and the vertical magnet advancesthe brushes of this selector S one step. Relay 10 in operating closes acircuit operates the above mentioned locking circuit for relays 13 and 5is opened at the armature and back contacts of this magnet. Relay 13will then release provided the relay 3 has again operated for the secondimpulse as both the locking circuit and the energizing circuit for thisrelay will be opened, the locking circuit is opened by the verticalmagnet and the energizing circuit is opened by relay As soon as thevertical magnet has taken one step, relay 14 operates from battery,winding of this relay, vertical ofi' normal contacts 15, lower armatureand front contact of relay 10 to ground at the left hand armature andfront contact of relay 5. Relays 5, 10, 12 and 14 will remain operatedduring the remaining impulses of the first digit. Relay 10 will remainoperated due to its slow-to-release characteristics. The vertical magnetwill respond each time relay 3 releases and relay 13 will be maintainedoperated during the release periods of relay 3 and release. as statedeach time the vertical magnet operates provided the relay 3 has operatedat this time. Relay 5 will therefore be positively locked during therelease periods of relay 3 under control of the vertical magnet.

\Vhen the impulses of the first digit have been sent and relay 3 isfinally operated, relay 10 will release due to the final release ofrelay 13. The release of relay 10 will also cause the release of relay12 to open the lookg circuit of relay 8. Relay 8 will therefore now beheld solely by the ground sup plied at the left hand armature and frontcontact of relay 3 and under control of relay 9. The release of relay 10closes a circuit for the rotary magnet which now will be operated tohunt for an idle second selector. This circuit for the rotary magnet 17may be traced from battery, winding of magnet 17 upper outer armatureand front contact of relay 14, lower normal contacts of relay 10 toground at the left hand armature and front contact of relay 3. Theoperation of magnet 17 opens the locking circuit for relay 14 at itsarmature and back contact to cause relay 14 to release and this relay inreleasing in turn opens the circuit for the rotary magnet. If now afirst selector is busy a ground will be supplied on the sleeve conductorthereof to cause the reoperation of relay 14 from battery, winding ofthis relay made vertical off-normal contacts 15, armature and backcontacts of magnet 17 second upper armature and'back contacts of relay 9to the sleeve conductor to ground of the busy selector. The operation ofrelay 14 will again close the above mentioned circuit for the rotarymagnet 17 to cause it to take another step and causethe release of relay14. This alternate operation and release of relay 14 and magnet 17 willcontinue as long as ground is found on the sleeve conductor of a busyselector.

When an idle selector is found relay 14 will not be operated andselector S will therefore stop on the terminals of this selector whichmay in this case be considered as the selector S1. Relay 9 will nowoperate over a circuit as follows: battery, winding of relay 14,vertical off-normal contacts 15, armature and back contact of rotarymagnet 17, winding of relay 9 to ground at the left hand armature andfront contact of relay 3. It should be noted that the reason relay 9 didnot operate as long as a ground was found on the sleeve conductor isthat this relay will be short-circuited by said ground. Relay 9 inoperating applies a busy ground to the sleeve of the selector S1 at itssecond upper armature and front contact. The operation of relay9 opensthe circuit for relay 8 and closes the tip and ring conductors of theselector S through to the selector S1 at its two upper armaturcs andfront contacts. The relay 8 does not release as it is slow in releasingand will be maintained by relay 12 which will be operated as soon asrelay 9 applied the busy ground to the sleeve. The operation of relay 9closes a circuit for relay 12 as follows: battery, vertical magnet 101,upper inner armature and back contact of relay 102, eleventh rotary stepcontacts 104, ring conductor of selectors S1 and S, third upper armatureand front contact of relay 9, inner upper make-before-break contacts ofrelay 19, upper inner armature and back contact of relay 20, upper innerarmature and front contact ofrelay 8, upper armature and back contact ofrelay 10, lower windof relay 19, upper winding of relay 12,

upper outer armature and back contact of relay 20, upper outermake-before-break contacts of relay 19, upper outerarinature and frontcontact of relay 9, tip conductor of selectors S and S1, upper outerarmature and back contact of relay 102, armature and back contact ofvertical magnet 101, winding of re lay 104, sleeve conductor ofselectors S1 and S. second upper armature and front contact of relay9 toground. Relay 12 in operating closes the above mentioned circuit formaintaining relay 8 operated. The vertical magnet 101 does not operatein this circuit. but relay 104 operates with relay 12. Relay 19 ispolarized and does not operate with the current in the direction astraced to this circuit, that is, with the battery on the ring con-sdoctors. The purpose of relay 19 will be explained in connection withthe application of ringing current. V p

The next series of dialing impulses will intermittently connect a groundto the ring conductor causing the vertical magnet 101 to operate. Thecircuit for the vertical magnet may be traced from battery through thewindings of magnet 101, upper inner armature and back contact of relay102, eleventh rotary step contacts 104, ring conductor of switches-S1and S, third upper armature and front contact of relay 9, upper1nake-before break contacts of relay 19,1.ipperinner armature and backcontact of relay 20, upper inner armature and front contact of relay 8,winding of relay 10,-left hand armature and front contact of relay 5,left hand armature and a b ack contact of relay 3 to ground or outerright hand armature and frontcontact of relay 13 to ground directly fromthewinding of relay 10 as relay 13' opera'tesoneach release of relay 3.Relay 106 also operated in this circuit, on the first release of relay8,

from battery, winding of relay 106, vertical off-normal contacts 107 tothe ground over the ring conductor. On the first step of switch S1 dueto the operation of the vertical A magnet 101 the circuit for relay 106'will be 6 shifted to be controlled over the'vertical 011 normal contacts107, armature and back contact of the rotary magnet 110, armature andfront contact of relay 106 to the ground on the sleeve supplied atthesecond upper armature and front contact of relay 9. Relay 104 releaseswhen the vertical magnet is operated as its circuit is controlledthrough the armature-and back contact of this magnet and when the seriesof impulses ceases relay 104 will again be operated. Relay 12 is heldoperated during the pulsing through the circuit completed by the innerlower contacts of relay 10 to ground at the right hand armature andfront contact of relay 5. The holdhand winding of relay 13, right handwinding of relay 5, inner right hand armature and front contact of relay13, second lower armature and front contact of relay 8, armature andback contact of magnet 11, upper inner armature and front contact ofrelay 9, upper outer make-before-break contacts of relay 19, upper outerarmature and front contact of relay 9, tip conductor of selectors S andS1, upper outer armature and back contact of relay 102, armature andback contact of magnet 101, winding of relay 104, sleeve conductor toground at the second upper armature and back contact of relay 9. Whenrelay104 operates it closes a circuit for the energization of the rotarymagnet 110 as follows: battery, windings of the rotary magnet 110, upperouter armature and front contact of relay 106, lower armature and frontcontact of relay 104, vertical ofi-normal contacts 107 to ground. Whenthe rotary magnet operates relay 106 releases, due to Eco opening of thecircuit therefor at the arma- T1'15 ture and back contact of magnet 110and this relay in turn opens the circuit for the rotary magnet 110 tocause it to release. If the first connector is busy the rotary magnet inreleasing will again close the circuit for relay 106 from'batterywindings of this relay, vertical off-normal contacts 107 armature andback contacts of magnet 110, upper armature and front contacts of relay104, lower armature and back contact of relay 102 to ground on winding.of relay contacts 114, fourth lower armature and,

winding of relay 111, vertical off-normal contacts 112, sleeve ofconnector C and selector S1, lower armature and back contact of relay102, winding of relay 102 to ground at the second upper armature andfront contact of relay 9.

Relay 102 in energizing applied at ground at its lower armature andfront contact to the sleeve of the connector C. Relay 106 does notoperate in the circuit in series with the winding of relay 102 frombattery winding of relay 106, off-normal contacts 107 armature and backcontact of magnet 110, upper armature and front contact of relay 104:,winding of relay 102 to ground at relay 9 as the resistancecharacteristics of the winding of relay 102 are such as to prevent it.Relays 102 and 10% are now held operated until the connection isreleased, the operation of relay 102 closing a holding circuit for relay10 1 from battery through a resistance and upper make-before-breakcontacts of relay 102, armature and back contact of the vertical magnet101, winding of relay 10 1 to ground at the second upper armature andfront contact of relay 9.

This direct ground applied to the sleeve of the connector C causes theoperation of relay 111 over the above traced circuit for this relay.Relay 111 did not operate in the above circuit when in series with relay102 due to the resistance characteristics of relay 102. Relay 111 in.operating closes a locking circuit for itself to ground at relay 102over its lower inner armature and front contact. Relay now operatesthrough the operation of relay 111, over a circuit from battery,

113, vertical off-normal front contact of relay 111, the sleeveconductor to ground at the relay 102. A circuit will thereby be closedfor maintaining relay 12 operated. It should be noted that relay 12 isslow in releasing so as to permit relays 111 and 113 to operate afterthe circuit for relay 12 has been opened by the operation of relay 102for again closing this circuit. lis circuit for rel y 12 maybe tracedfrom battery, winding of vertical magnet 115, lower armature and frontcontact of relay 113, third upper armature and back contact of relay116, ring conductor from the connector 0 to the selector S1, inner upperarmature and front c fact of relay 102, 11th rotary step contacts ringconductor to the selector S, third upper arniat re and front contact ofrelay 9, inner upper PJQlIG-lJQfOIG-blfiilk contacts of relay 19, upperinner armature and back contact of relay 20, upper inner armature andfront contact of relay 8, upper armature and back contact of relay 10,lower winding of relay 19, upper winding of relay 12, upper outerarmature and back contact of relay 20, upper outer make-beforebreakcontacts of relay 19, fourth upper armature and front contact of relay9, tip conductor to switch S1, upper outer armature and front contact ofrelay 102, tip conductor to connector G, fourth upper armature and backcontact of relay 116, upper inner armature and back contact of therotary magnet 118, armature and back contact of vertical magnet 115,winding of relay 120, second lower armature and front contact of relay111, sleeve conductor to ground at the lower armature and front contactof relay 102. Relay 12 is thereby maintained operated to hold relay 8operated through its locking circuit.

The circuits are now ready for the sending I of the third digit. Relayis operated in the above mentioned circuit but releases as soon as thevertical magnet is operated and remains released during the sending ofthe vertical impulses. The release of relay 3 in response to the firstimpulse closes a circuit from ground at the left hand armature and backcontact of this relay, left-hand ariature and front contact of relay 5through the winding of relay 10, back over the tip eonductor through theswitches S3, S1 and C through the winding of the vertical magnet 15 tobattery over the connections hereinbefore described. This causes theoperation of relay 10 which opens the circuit for relay 12 but thisrelay is maintained operated during the operation of relay 10 over acircuit as hereinbefore described through the lower inner contacts ofrelay 10 to ground at the right-hand armature and front contact of relay5. Relay 10 remains operated as usual during the sending of the pulses.The relay 120 as stated, releases not only due to the opening of thecircuit through the upper armature and back contact of relay 10 but alsothrough the opening of a circuit through the armature and back contactof vertical magnet 115. The usual holding circuit for relays 13 and 5while the pulsing relay is released may be traced in this case frombattery through the left hand winding of relay 13, right hand winding ofrelay 5, inner right hand armature and front contact of relay 13, secondlower armature and front contact of relay 8, armature and front contactof vertical magnet 11, upper inner armature and front contact of relay9, upper outer makebeforc-break contacts of relay 19, over the abovetraced connection for the tip conductor through selector S1 andconnector C and upper inner armature and front contact of rotary magnet18 and armature and back contact of the vertical magnet 15 to the groundat relay 102. This holding circuit is thereforedependent upon theoperation of vertical magnet 15 in the same manner as it was dependentupon the operation of the vertical magnet 11 in selector S and thevertical magnet 101 in selector S1. The resistance of the windings ofrelays 13 and 5 prevent and front contact, lower outer armature and backcontact of relay 120 through the ver-v tical off-normal contacts 11 l tground.

terminals of the wanted subscribers line;

' ated and relay 10 will operate during the 7 cause the release of relay113.

When the last impulse in this digit has been sent relay 120 will againoperate and thereby The circuits are now ready for the reception of thelast digit. v

The release of relay 11 8v closes a circuit for the rotary magnet 118from battery, winding of this magnet, lower armature and back contact ofrelay 113 over the same circuit as was hereinbefore traced for thevertical magnet 115 and the impulsesv in this last digit will nowoperate the rotary magnet to ad vance the switches to the desired partyline The relays 12 and 8 will be maintained operpulsing while theholding circuit for relays .13 and 5 will pass through the inner upperarmature and front contactof magnet 118 and depend upon the operation ofthis mag net in the same manner as it was depending upon the operationof the vertical magnet 115. Relay 120 releases during the sending ofthe'pulses in this digit in the same manner as during the sending of thepulses for the vertical magnet and is operated again when the pulsingceases. I 1

It should be notedithat' relay 122 is operated when the rotary magnet isoperated overv an obvious circuitto prepare the connector for a busytest When the rotary magnet ceases to operate. On the last step of therotary magnet relay 122 will not release if the desired line is busy asa ground will be found on the sleeve terminal of this line. This groundcloses a locln'ng circuit for relay 122 before it has time to releasefrom battery lower winding of relay 122 and its lower inner armature andfront contact, upper make-be fore-break contacts of relay 120 before itis actuated at the end of the series of the'rotary magnet impulses,lower outer armature and 1 front contact of relay 111'to ground on thesleeve of the wanted line. When relay 120 operates, this locking circuitis transferred through the upper outer armature and front contact ofrelay 120, lower winding of relay 116, lower inner armature and frontcontact of relay 120 to ground. Relay 116 is operated in this circuitand looks from battery through its upper winding and upper innerarmature and front contact to ground J at relay 120. Relay 116 inoperating removes battery and'ground connections from'the tip and ringconductors towards the selectors S1 and S. due to the opening of theconnections for these conductors at the third and fourth 7 upperarmatru'es and'back contacts of this relay. This 'causes the release ofrelays 12 and 8; However, the operation of relay 116.

connects a battery through aresistance to the tip conductor for theoperation of relay 20. This circuit maybe traced from' battery ing ofrelay 120, inner upper armatureand back contact of relay 12, third lowerarmature and front contact of relay 8, before this relay is releasedafter the release of relay 12, lower make-b-efore-break contacts ofrelay 10,

left hand armature and front contact of red lay 3 to'groundQ Relay 20 inoperating provides a locking circuit for itself from ground through itsupper outer armatureand front contact over the tip conductor to the battery applied by relay 116. Relay 20in'operating applies a busy tone fromsource 22 through thelower armature and front contact of relay 20, lowerinner armature and front contact of relay 9 to the'tip conductor leadingthrough the line finder LF to the calling subscribers station.

If the called subscribers line'is' not busy there is no ground on thesleeve of his line and therefore relay122 willrelease. However, acircuitis completed for the operation of relay 116 after the operationofrelay 120 asfollows: Battery through the line relay of the calledline'ov'er the sleeve conductor,

lower outer armature and front contact of relay l11, lower outerarmature and back contact of relay 122, inner upper armature and frontcontact of relay 120, lower winding of relay 116 and to ground on thelower inner armature and front contact of relay 120. Relay 120 ismaintained operated after relay 116 is operated althoughthe originaloircuit'for' this relay is opened. The new circuit for relay 120 may betraced from battery through a resistance, upper make-beforebreak contactof relays 111 and 116,=upper inner armature and back contact of rotarymagnet 118, armature and back contact of vertical magnet 115, winding ofrelay 120. second lower armature and front contact of relay 111 to theground at relay 102. The operation of relay 116 opens the connection tobattery and ground for the tip and ring conductors to cause the releaseof relays 12 and 8but there is no battery supplied on the tip conductorin this case as relay 122 is released and therefore relay 20 will notoperate. Instead ringing current is applied to the called subscribersline in this case from the negative source at 23, second lower armatureand back contact of relay 19 upper winding of ringing trip relay 24,inner lower armature and back contact of relay 19, upper armature andback contact of relay 24, over the tip conductor through switches S, S1and the connector C to the tip conductor of the called subscribers lineand through his bell and back over the ring conductor through theconnector C, selectors S1 and S through the upper outer armature andback contact of relay 24 to ground. When the called subscriber removeshis receiver in response to this ringing signal relay 24 operates andopens the ringing circuit. This relay in operating closes a lockingcircuit for itself from battery through its lower winding and lowerarmature and front contact to ground at the left hand armature and frontcontact of relay 3. The operation of relay 24 also establishes aconnection through its upper armatures and front contacts to battery andground for the tip and ring conductors through the windings of relay 4which now operates through the called subscribers loop and reverses atits left-hand armatures and contacts the connection from battery andground through the windings of relay 3 to the calling line. Talkingbattery for the calling subscriber is supplied from battery and groundthrough the winding of relay 3 and talking battery for the calledsubscriber is supplied from battery and ground through the windings ofrelay 4.

To'select and ring a desired subscriber on a four party line, theconnectors C may be segregated in two groups either one of which may beselected by the selector S1. In one group the tip and ring conductorsare shown as in connector C and in the other group the tip and ringconductors are reversed as indicated at the terminals 126. The conditionof the tip and ring conductors in this respect will determine thepolarity of ringing current to be applied to the called subscribersline. A selected connector may then select either one out of two sets ofterminals associated with a called party line arranged as shown at 128and thereby causes the signaling current ofone polarity or the other tobe applied to one side or the other of the party line 100 to ring thedesired subscribers bell. These bells are connected as shown with likebells of two subscribers responsive to opposite polarities of signalingcurrent connected to each side of the line.

As hereinbefore described, ringing current .from source 23 was suppliedwhen relay 19 the selectors S1 and S and thereby caused relay 19 whichis polarized to operate in series with relay 12. A holding circuit forrelay 19 which may be traced from battery through the upper winding ofthis relay and its lower outer armature and front contact to the groundat the right hand armature and front contact of relay 5 will maintainthis relay operated as long as the connection remains. Relay 19 inoperating reverses the connections for the tip and ring conductors atits upper armaturcs and front contacts. The operation of the system inregard to the operations of the vertical and rotary magnets in theselector S1 and connector C and the maintaining of the holding circuitfor relays 13 and 5 during the pulsing will be exactly the same ashereinloefore described. The currents for the impulses will, however,pass over the tip and ring conductors in the reverse order between theconnector C and the selector S but at connector C and selector S thecurrent will pass in the same direction as hereinbefore described whenrelay 19 is not operated and the tip and ring conductors are notreversed in the connector. When the connection has been established to acalled subscribers line and ringing is applied with relay 19 operated,

ringing current will be supplied from the positive source 26 through thelower outer armature and front contact of relay 9, lower inner armatureand front contact of relay 19, upper Winding of relay 24, second lowerarmature and front contact of relay 19, upper outer armature and backcontact of relay 24 to the tip conductor. At relay 19 and its innerlower armatures and front contacts the ringing current will betransferred to the ring conductor and will continue over this conductoruntil itreaches the connector C where it is again applied to the tipconductor. Depending therefore on whether the current is received fromthe negative source 23 or the positive source 26 and whether theconnector C has established connection with the called line 100 at theupper set of terminals or lower set of terminals at 128, thecorresponding desired party line subscribers bell will be actuated.

When the connection is released by the calling subscriber hanging up hisreceiver, the relay 3 in releasing causes the release of relay 5 andthis relay in releasing opens the holding circuit for relays 24 and 9and if relay 19 is operated the holding circuit for this relay will alsobe opened. A circuit for release magnet 28 will now be closed frombattery winding of this magnet, the vertical off-normal contacts 15,left-hand armature and back contacts of relays 5 and 3 to ground torelease the selector S to normal when the release circuit is opened atthe vertical off-normal contacts 15. Then relay 9 releases the holdingground is removed from the sleeve of selector S1 to cause the release ofrelays 104 and 102 and close a circuit for the release magnet 130 frombattery through the winding of this magnet, middle upper armature andback contact of relay 106, lower armature and back contact of relay 104to the vertical oflf-normal contacts 107. Selector S1 is therebyreleased and when it has returned to normal the circuit for the releasemagnet 130 is opened at the vertical off-normal contacts 107. .Theremoval of the ground from the sleeve at selector S1 by the release ofrelay 102 will release relays 111 and 120 and relay 120 in releasingwill release relay 116. A. circuit for the release magnet 132 is therebycompleted from battery, winding of this magnet, second upper armatureand back contact of relay 116, third lower armature and back contact ofrelay 111, lower outer armature and back contact of relay 120 to groundat the vertical old-normal contacts 114. The connector C is 1 therebyreleased and the release circuit is opened on the return of theconnector to normal by the opening of the connection to ground at thevertical oil-normal contacts 114.

While this invention has only been illus+ trated in connection with asingle system it should be understoodthatit may readily be applied to aplurality of other systems with out departing from the spirit thereof.

What is claimed is: v

1. In a telephone system, a switching de vice, van operating magnettherefor, a. hold ing relay,'a pulsing relay controlling said magnet,means for operating said holding relay responsive to, the operationofthe pulsing relay, and means for locking said holding relay in operatedcondition under control of the operating magnet.

2. In a telephone system, a switching device, an operating magnet forsaid device, a

holding relay, a pulsing relay controlling the operations of saidholding relay and said operating magnet, a locking circuit controlled bythe operating magnet for maintaining said holding relay operated whilethe pulsing relay is released. I

3. Ina telephone system, a switching de-' vice, an operating magnettherefor, a holding, relay, a pulsing relay, means for operating saidholding relay in response to the operation of the pulsing relay, meansresponsive to the release ofthe pulsing relay for locking the holding.relay in operated condition, means responsive to the holding relay andrelease of the pulsing relay for actuating said magnet, and meansresponsive to the operation of the magnet for disabling said lockingmeans.

4. In a telephone system, a switching vice, an operating magnet, aholding relay having two windings, a pulsing relay,-means responsive tothe operation of the pulsing relay for establishing an energlzingcircuitfor said holding relay through one winding? thereof, means forestablishing a. locking circuit through the other winding of saidholding relay in response to the release of the.

pulsing relay, means for establishing an ener-' gizing circuit for theoperating magnet in response to the release of the pulsing relay and theoperation of the holding relay, and.

through the other winding of said holding,

relay in response to the release of the puls-v ing relay, means forestablishing an energia 111g circuit for the operating magnet 1nresponse to the release of the pulsing relay and the operation of teeholding relay, and means for opening said locking circuit in response tothe actuation of the magnet.

6. In a telephone system, a switching device, an operating magnet, aholding relay, a pulsing relay for controlling said operating magnet,means for operating said holding relay while the pulsing relay isoperated, another relay, means for operating said second relay inresponse to the release of the pulsing relay and operation of theholding relay, means responsive to the operation of said second relayfor establishing a'locking circuit for the holding relay, means foropening said locking circuit in response to the operation of the magnet.

7.111 a telephone system, a switching de vice, an operating magnet, aholding relay, apulsing relay for controlling said operat ing magnet,means for operating said holding relay while the pulsing relay isoperated, another relay, means for operating said relay and saidmagnetin response to the release of the pulsing relay and the operationof the holding relay, means responsive to the operation of said secondrelay for establishing a locking circuit for the holding relay andlished and by current from the source in the to party lines, precedingswitches for connecting calling lines with idle switches in any of saidgroups of switches for establish ng connections to party lines, sourcesof signaling 1 current of different characteristics associated with thepreceding switches for calling connected party lines, a source ofcurrent in each of said group switches, means depending on the group ofswitches through which the conneetion is established by a switch thereofand controlled by the source of current in the group switch throughwhich the connection is established for selecting a particular signalingsource, and means in the preceding 26 switch responsive to thecompletion of the 7 connection to the desired party line for applyingsignaling current thereto from the selected source.

10. In a telephone system, calling lines,

Lv party lines, groups of final switches having access to party lines,preceding switches for connecting calling lines with party lines toswitches in said groups, sources of signaling current of differentcharacteristics associated with said preceding switches for signalingparty lines, a source of current in each final switch, means forselecting the signaling source to be used responsive to the selection ofthe group in which the final switch used in establishing a connection islocated and to current from the source in said final switch, a relay inthis final switch operative on the completion of the connection andmeans in the preceding switch used in the connection responsive to theoperation of said relay for applying signaling current from the selectedsource to the connected party line.

11. In a telephone system, calling lines, party lines, groups of finalswitches having access to said party lines, preceding switches forconnecting calling lines with party lines through final switches,sources of signaling current of different characteristics associatedwith preceding switches for signaling party lines, relays in thepreceding switches for controlling the selection of a signaling source,a current source in each final switch, means responsive to theestablishing of a. connection from a preceding switch to a final switchof one group and to current from the source in said final switch forcontrolling the relays in said connected preceding switch to select onesignaling current source and responsive to a final switch of anothergroup and to current from the source in said last mentioned final switchfor controlling the relays in the connected preceding switch to selectanother signaling current source and means responsive to theestablishing of a connection to a party line for transmitting currentfrom the selected signaling source. I

12. In a telephone system, calling lines, party lines, groups of finalswitches having access to said party lines, preceding switches forconnecting calling lines with party lines through final switches,sources of signaling current of different characteristics, means forestablishing certain potential conditions on the conductors from thefinal switches in one group to preceding switches connected thereto andfor establishing certain other potential conditions on the conductorsfrom the final switches in another group to preceding switches connectedthereto, means in a preceding switch responsive to the potentialconditions established from a connected final switch for selecting acorresponding signaling source, and means for applying current from saidselected signaling source to a connected party line in response to theestablishing of the connection thereto.

13. In a telephone system, calling lines, party lines, groups of finalswitches having access to said party lines, preceding switches forconnecting calling lines with party lines through final switches,sources of signaling current of different characteristics, means forestablishing certain potential conditions on the conductors from thefinal switches in one group to preceding switches connected thereto, andfor establishing certain other potential conditions on the conductorsfrom the final switches in another group to preceding switches connectedthereto, means including a relay in a preceding switch controlled by thepotential conditions on the conductors from the connected final switchfor selecting a corresponding signaling source, and means for applyingcurrent from the selected signaling source to the connected party linein response to the establishing of the connection thereto.

141. In a telephone system, calling lines, called lines, trains ofswitches for connecting a calling line with a called line, means in thelast switch used in establishing a connection for applying battery tothe tip conductor of the preceding switches in response to the callingline being already engaged in a pre- 1 vious connection, and means in apreceding switch responsive to this battery connection for applying busytone to the calling line.

15. In a telephone system, calling lines, called lines, trains ofswitches for connecting a calling line with it called line, a connectionto battery and ground for the last switch used in the establishing of aconnection, means in the last switch for momentarily opening theconnection to battery and for permanently opening the connection toceding switches, and means in a preceding ground in response to thecalled line being busy, and means'in a preceding switch responsive tosaid momentary removal of the battery connection and the permanentremoval of the ground connection for applying busy tone to the callingline. 7

16. In a telephone system, calling lines, called lines, trains ofswitches for connecting a calling line and a called line, means in thelast switch used in the establishing of a connection for normallyconnecting battery and ground to the tip and ring conductors for thepreceding switches, a relay in said last switch, means for operatingsaid relay during the operation of said last switch in search of thecalled line, means for releasing said relay if the called line whenfound is idle and for maintaining it operated if the called line isbusy, means responsive to the maintaining of said relay operated at thistime for momentarilyremoving the battery connection and permanentlyremoving the ground connection for the preceding switches and means in apreceding switch responsive to said removal and subsequent restorationof the battery connection and removal of the ground connection forapplying a busy tone to the calling line.

17. Inatelephonesystem,callinglines,called lines,trains of switchesforconnectinga calling line and a called line, means in the last switchused in the establishing of a connection for normally connecting batteryand ground to the tip and ring conductors for the preceding switches, arelay in said last switch, means for operating said relay during theoperation of said last switch in search of the called line, means forreleasing said relay if the called line when found is idle and formaintaining it operated if the called line is busy, means responsive tothe release of said relay at this time for extending connection to thecalled line over the tip and ring conductors thereof and for removingthe battery and ground connection from the preceding switches, means ina preceding switch responsive to the removal of battery andgroundconnection for applying ringing signals to the called lines, meansresponsive to the maintenance of said relay operated for momentarilyremoving the battery connection and permanently removing the groundconnection for the preswitch responsive to said momentary re moval ofthe battery connection and the permanent removal of the groundconnection for applying a busy tone to the calling line.

18. In a telephone system, calling lines,

called lines,trains of switches for connecting a calling line and acalled line, means in the last switch used in the establishing of, aconnection for normally connecting battery and ground to the tip andring conductors for during the operation of said last switch in searchof the called line, means for releasing said relay if the called linewhen found is idle and for maintaining it operated if the called line isbusy, means responsive to the maintaining of said relay operated at thistime for momentarily removing the battery connection and for permanentlyremoving the ground connection to the preceding switches,

and means including a relay in a preceding H) switch responsive to saidmomentary removal of the battery connection and the permanent removal ofthe ground connection for applying busy tone to the called line.

19. In a telephone system, calling lines, called lines, trains ofswitches for connecting a calling line with a called line, means in thelast switch used in establishing a connection including two relaysresponsive to the called line being already engaged in a pre' viousconnection for applying battery to the tip conductor of the precedingswitches, and means including a relay in a preceding switch responsiveto this battery, connection for applying busy tone to the calling line.

20. In a telephone system, calling lines, called lines, trains ofswitches for connecting a calling line with a called line, means in thelast switch used in establishing a connection for normally applyingbattery and ground to the tip and ring conductors of preceding switchesand for momentarily removing said battery connection and for permanentlyremoving the ground "connecmentioned relays and before the release ofthe other, and means for applying busy tone to the calling subscriber inresponse to the operation of said last mentioned relay.

In witness whereof I hereunto subscribe my name this 24th day of July,1930.

RAY L. STOKELY.

the preceding switches, a relay in said last 7 .switch, means foroperating said relay

